Piston ring



April 4, 1944. Q N EL Ag 2,345,589

PISTON RING Filed Oct. 21. 1940 2 Sheets-Sheet 1 1 INVENTOR. .4 CARLRENGELHARDT ATTORNEY.

April 1944- c. F. ENGELHARDT 2,345,589

PISTON RING 2 Sheets-Sheet 2 Filed Oct. 21. 1940 Mill II II II 5/ a V 85I 5/ 34 J INVENTOR.

g3 48 BY CARL F. ENGELHARDT Patented Apr. 4, 1944 V UNITED STATES PATENTOFFICE PISTON RING Carl F. Engclhardt, Yeadon, Pa., minor to WilkeningManufacturing Company, Philadelpliia. Pa., a corporation of DelawareApplication October 21, 1940, Serial No. 362,119 9 Claims. (Cl. 309-45)The present invention relates to a self-expandof the present inventiondisposed in each of the ing piston ring and it relates more particularlythree ring-receiving grooves thereof. to a self-expanding piston ringwhich is prefer- Figure represents a perspective view of a ably made ofsheet metal, and so formed, confragmentary portion of a sheet metalblank in structed, and arranged as to present two rela- 6 its fiatcondition of which the piston ring of the tively narrow parallel annularcylinder-contactpresent invention may be formed, but before the ingsealing surfaces composed of a multiplicity cylinder-contacting elements22 and 23 have been of sector-like sections disposed end to end in bentover and before the spring-forming elements close proximity to eachother so as to constitute 25 thereof have been formed or shaped into themore orless continuous annular cylinder-contact- 10 springs 5|intervening the cylinder-contacting ing surfaces with but a very smallgap between elements 22 and 23. the sectors, and spring means forming anin-. Figures 6 and 7 represent a front view and a tegral part of thepiston ring and also prefertop elevational view, respectively, of afragmenably formed of the same sheet metal of which tary portion'ofastrip of piston ring material like the cylinder-contacting 'elements areformed, that shown in Figure 5, but after the cylinderthereby to tend toexpand the ring tangentially contacting elements 22 and-23 have beenbent or circumferentially with a resultant radially outover and afterthe intervening spring-forming ward expansion of the componentcylinder-conportions 25 have been formed into the generally tactingelements thereof. U-shaped springs 5|, but before the strip has Thepresent invention is a. modification and 20 been completely formed intothe arcuate formaimprovement of the construction shown in aption by thefurther collapsing of the U-shaped plicants co-pending applicationSerial No. spring members 5|.

321,200, filed February 28, 1940. Figures 8 and 9 represent a frontelevational The piston ring of the present invention may view and a topplan view, respectively, similar to be used both for oil controlpurposes in the bot- 5 that shown in Figures 6 and 7, but after thestrip tom ring-receiving groove of a piston which has has been formedinto the generally arcuate form apertures, through the piston wall foroil draincorresponding generally to the curvature of the age and whichmay also be used'in the upper cylinder in which the piston ring is to beused,

ring-receiving grooves without any oil drain holes by further collapsingthe generally U-shaped through the piston wall, for compression purospring members 5| and by bringing the juxtaposes. posed radial edges 44and 45 of the cylinder- For the purpose of illustrating the invention,contacting elements 22 and 23 into correspondthere is shown in theaccompanying drawings ing proximity to each other. forms thereof whichare at present preferred, Figure 10 represents a perspective view,simisince the same have been found in practice to lar to that of Figure5, of a sheet metal blank give satisfactory and reliable results,although it in which the extensions 10 and 1| have been omitis to beunderstood that the various instrumented from the spring-formingelements 25.

'talities of which the invention consists can be Figure 11 represents aperspective view simivariously arranged and organized an that the lar tothat of Figure 2 of the embodiment shown invention is not limited to theprecise arrangein igure 10. ment and organization of theinstrumentalities One form or embodiment of the present inas hereinshown and described. vention is illustrated in Figures 1 to 9,inclusive, In the accompanying drawings in which like the formation ofwhich is illustrated in Figures reference characters indicate likeparts, 5 1 S1 Figure 1 repre ents a to lan iew of a pi ton Thus, in thisembodiment Of the present invenring embodying the present invention ahow tiOn, a flat Sheet-meta] of suitable installed in a piston disposedwithin a cylinder, ness having an aggregate width is out out in which isgenerally on line l-l of Figure 3 (the ggf igiiz ggzfig g i f' gg P 55525? 2 parts not being in true proportion, for purposes of btterillustration). tor-shaped, cylinder-contacting elements 22 and Figure 2is a perspectiv view of a fragmenzig fi is ggfifi ggg g gfigfi gg pomonstary portion of the piston ring of the present in- The sprmkformmgportions 25 are r'elatlvely ven'tion on a much enlarged scale with a.portion nan-0w strips of metal formed on the center line broken awaybetter to expose to view some of of the total width 2| of the strip gmthe internal details of construction. By r a n of th fact that thspring-form- Fi ure 3 epresents a section on line -3 1 ing element 25when finally made into the spring Figure 2. member 51 in the finalpiston ring, will occupy Figure 4 represents a sectional view of theuponly a relatively small portion of the total area per portion of apiston showing the piston ring so of the black well, said black wallwill be in most part an opening beneath said spring member 5|. Thisaperture is advantageous when the piston ring is used for oil controlpurposes in one or two of the lower ring-receiving grooves 21 of athree-groove piston such as is illustrated in Figure 4, or of afour-groove piston wherein the lowermost or the lower two ring-receivinggrooves are provided with oil drain holes 28 extending through thepiston wall 29 for oil draining purposes. The piston ring may also beused unchanged for compression purposes in the uppermost ring-receivinggroove 30 of the piston 3| or in the upper two-ring receiving grooves 30and 32 as shown in Figure 4.

The upper and lower cylinder-contacting portions 22 and 23 respectivelyextend circumferentially in opposite directions thereby producing astaggered or offset effect as indicated particularly in Figures 5, 6, 7,8 and 9 so that the edges 44 and the edges 45 are not directly inalignment with each other, thereby tendingto minimize even a tendency toblow-by. If desired, this staggering may be less accentuated than thatshown in the drawings.

The longitudinal or circumferential width of the cylinder-contactingportions 22 and 23 is slightly smaller in the base dimension 42 than inthe end dimension 43 or in the circumferential dimension 43, thisdifference being so calculated that when the cylinder-contactingelements 22 and 23 have been bent over and have been brought generallyto edge-to-edg as indicated in Figures 1, 2 and 9, the juxtaposed edges44 and 45 will parallel each other and will be disposed as radii inrelation to the axis or center 46 of the piston.

The spring-forming portions 25 areformed with the shoulder or extensionsand H as shown in Figures 2, 5, 6 and 8, these extensions serving assupports for the cylinder-contacting elements 22 and 23 in the pistonring as finally formed, this being shown in Figures 2 and 8. Theextensions 10 and Il may be omitted, however, as is shown in Figures 10and 11.

The peripheral or cylinder-contacting edges or surfaces 41 and 48 of thecylinder-contacting elements 22 and 23 respectively, may also be given aslightly convex arcuate curvature between the ends 49 and 50 thereofcorresponding to the curvature of the cylinder in which the piston ringis intended to be used, so that when the cylinder-contacting elements 22and 23 are placed side by side in close proximity as indicated inFigures 1, 2 and 9, the successive, adjacent, cylinder-contactingsurfaces 41 and 48, respectively, will form corresponding true circlesmatching the circle of the cylinder.

The formation of the blanks shown in Figure 5 may be accomplished bypunching operations on any suitable punch press, either manual orsemi-automatic, or fully automatic, with suitable dies and puncheseither by step-by-step or progressive punching operations. However, ifdesired, the blanks shown in Figure 5 may also be formed by milling outthe portions 33 and 34 or by cutting out the portions 33 and 34 on ashaper or on a breaching machine. If the portions 33 and 34 are to becut out on a milling machine or on a shaper or on a broaching machine,several sets may be stacked together and may be milled, shaped orbroached all together gang-wise.

The piston ring is formed by bending over towards each other thejuxtaposed cylinder-contacting elements 22 and 23 so that they more orless parallel each other as indicated in Figures 6, '7, 8 and 9 and alsoin Figure 2 and by corrugating or bending the spring-forming elements 25in a generally radial direction to form a series of spacedcorrugation-like or loop-like springs 5|.

The formation of the piston ring from the blank shown in Figure 5 may beaccomplished by successive bending operations performed in any suitablesequence where all the bending operations may be done more or lesssimultaneously to produce the result indicated in Figures 1, 2, 8 and 9.In Figures 6, '7, 8 and 9, however, I have illustrated what may be onedesirable sequence of bending or forming operations although it is to beunderstood that this sequence may be changed, or the bending or formingoperations may all be accomplished more or less simultaneously bysuitable automatic or semiautomatic bending and forming jigs or fixturesor machines.

Thus, for instance, in Figures 6 and 7, I have illustrated what, may bean initial stage in the formation of the piston ring wherein thecylinder-contacting elements 22 and 23 have been bent over to paralleleach other and wherein the spring-forming portions 25 have been bentinto an initial U-shape formation 52 preliminary to their formation intothe more closed loop-shaped spring 5| shown in Figures 8 and 9. In thiscondition, the piston-ring-forming strip would be generally straight asindicated in Figure '7, with the juxtaposed edges 44 and 45substantially separated from each other and in non-parallel relation.Thereafter, the generally U-shape formations 52 may be collapsedsomewhat to form the more or less loop-like springs 51 with a relativelysmaller gap 53 between their free ends 54 and 55; the gap 53 beingsufficient, however, so that the ends 54 and 55 will not quite toucheach other when the juxtaposed radial edges 44 and 45 of thecylinder-contacting elements 22 and 23 have actually contacted eachother. By this final collapsing operation the piston ring material orstrip is formed in a generally arcuate shape indicated in Figure 9generally corresponding to the curvature of the cylinder in which thepiston ring is to be used.

In the commercial manufacture of piston rings accordin to the presentinvention, the blank shown in Figure 5 as well as the correspondingpiston ring strips shown in Figures 6, 7, 8 and 9 may be formed more orless continuously in relatively great length from which smaller piecesmay then be cut off after the strip has been completely formed or shapedinto the form shown in Figures 6 and 7, or even after it has been formedinto the curved shape shown in Figures 8 and 9. The length of theindividual pieces would correspond more or less accurately to thecircumferential dimension of the piston ring desired. For the difierentsized piston rings the other dimension would also be varied to accordwith the width of the ring-receiving group, the depth of thering-receiving group, and the diameter of the piston.

Thus, for instance, the individual pieces corresponding to thecircumferential length of the piston ring could be cut off while thestrip is straight as in Figures 6 and 7 and then the shorter piececurved and completed to the form shown in Figures 8 and 9 and in Figures1 and 2, or the strip can be curved while it is still part of the wholepiece of considerable length and formed into a generally spiralformation as it is being assasso curved and thereafter individual piecescut of! corresponding to the circumferential length of the desireddiameter.

In making the piston ring, the spr n members II are collapsed until thejuxtaposed edges 44 and I! meet each other or abut each other, therebyproducing the curved shape. However, when the compression pressure isreleased, the spring members Ii open up slightly or spring back slightlyso that the edges 44 and ll separate from each other slightly asindicated in Figures 2, 8 and 9. However. the circumferential length ofthe piston ring is so adjusted that when the free ends it and ill of thepiston ring abut each other and the ring is compressed circumferentiailyor tangentially into the diameter of the cylinder II, the radial edges Nand 45 f the cylinder-contacting elements 22 and 22, respectively, willgenerally abut each other or will have but a very small clearanc betweenthem. It is estimated that the total or aggregateof all clearancebetween the successive pairs of edges 44 in the entire circumference orbetween the successive pairs of edges 45 in the entire circumference maybe a few thousandths of an inch, perhaps .003" to .007", more or less(that is, an amount perhaps no greater than the clearance at the gap inan ordinary piston ring): it being understood that at the gap or breakOI there would be substantially no clearance as the edges II and II willabut each other. Thus, by reason of the fact that each of the bends orspring members tends to open up slightly after the ring has beencompressed into the cylinder as is indicated in 1'18- ure 1, there is auniformly distributed, tangential or circumferential force betweensuccessive sections of the piston ring, that is, between successive oradjacent cylinder-contacting elements 22 and 23, respectively, and thisforce is in turn translated into an outward radial component forcetending to force each of the cylinder-contacting elements radiallyoutward and tending to press the cylinder-contacting edges 41 and 48thereof into ilrm contact with the cylinder wall with a uniformlydistributed and predetermined radial force. By reason of the fact thateach pair of cylinder-contacting elements 22 and 23 is free to moveradially inward or outward, more or less independently of other pairs ofelements,

the ring is.capable of adjusting itself to irregularities in thecylinder wall, such as are produced by prolonged operation 01' themotor. As a result, the piston ring of the present invention is moreefllcient in preventing loss of power ordinarily resulting fromirregularities in th cylinder wall and is, in addition, more efficientin preventing leakage of oil through suchirregularitfes up into thecombustion chamber of the cylinder, thereby materially reducing oilconsumption in such worn motors.

It will be noticed that the edges 41 of the cylinder-contacting elements22 and the edges 48 of the cylinder-contacting elements 23 overlap thegenerally U-shaped or generally loop-shaped spring member 5| to a slightextent.

In the manufacture of the piston ring of the present invention, I-mayalso grind-finish the cylindrical periphery 59 of the completed ring byclamping the finished ring axially between,

suitable supporting discs upon a suitable mandrel or any suitablefixture, while the ring is generallyfully compressed, and then grindingthe periphery 58 to match the cylinder, by rotating the ring about itsaxis against a revolving grinding wheel. If desired, a number of pistonrings may be so clamped and held side by side on the same fixture or onthe same mandrel between the same clamping discs or blades, so that theymay be ground altogether to match the cylinder.

The piston ring of the present invention is highly effective both foroil control as well as for compression, and may be used without anyseparate expander spring and will produce a suitably highcylinder-contact pressure per unit or area betweenthecylinder-contacting surfaces. of the piston ring and the cylinder wall.However, the resilient strength of the spring member ii is adiusted toprevent too-high cylinder-contact pressure so that there will be noscoring of the cylinder wall and so that there will be little variationin the pressure of size ranging from standard diameter to slightlyoversize (.060 oversize, for example).

The piston ring of the present invention is preferably made of sheetsteel of suitable consistency or suitable hardness although it may bemade of other sheet metals, such as sheet bronze or sheet brass or othersuitable alloy, both ferruns and non-ferrous. If the piston ring is madeout of sheet steel, it may be formed out or fully annealed sheet steelbut one capable of being subsequently hardened and tempered to asuitable degree of hardness and also to impart a suitable degree ofresiliency to the spring members ll. Thus, for instance, the blank shownin Figure 5 may be formed while the metal is completely annealed and theformation shown in Figures 6 and 7 and even the formation shown inFigures 8 and 9 may be made while the metal is fully annealed, althoughthese formations may also be formed with a certain amount of hardnesssetting into the metal by suitable hardening and tempering. The finalhardening and tempering, however, should preferably be done before thecylindercontacting circumference of the completed ring is grind-finishedor otherwise finished to the cylinder diameter. y

The piston ring of the present invention is particularly eillcient inpreventing an excessive pressure upon and scoring of the cylinder walland in providing a high degree of oil drainage. As describedhereinbefore, that portion of the back wall directly opposite each ofthe spring-forming members Si is completely open and the piston ringthereby permits of very efficient drainage of oil therethrough.

It is possible to make one of the cylinder-contacting elements 22 or 22of a shorter length than the other so that it does not actually makecontact with the cylinder, and it is further possible to omit one ofsaid elements completely. In such a case, each piston ring would presentonly ,a single narrow annular rib making contact with the cylinder: thespring members 5| then merely acting as a supporting ring and spacingring.

The present invention may be embodied in ;other specific forms withoutdeparting from the a spirit or essential attributes thereof, andit istherefore desired that the present embodiment be considered in allrespects as illustrative and not restrictive, reference being had to theappended claims rather than to the foregoing description to indicate thescope of the invention.

It is pos ible to have the cylinder-contacting elements 22 and 23ii-shaped instead of L-shaped.

-It is also possible to have the base of the L (or the T) a relativelynarrow strip so that the cylinder-contacting ribs in the final ring willbe continuous only along the outer periphery with relatively narrow,circumferentially separated, radially inward extensions connecting theouter periphery to the troughs.

Having thus described the invention, what is hereby claimed a new anddesired to be secured by Letters Patent is:

l. A one-piece, flexible, self-expanding piston ring comprising acentral, corrugated annulus composed of alternating crests and troughsof spring material extending in a generally radial direction, saidcrests being radially outermost and consisting oi relatively narrowstrips placed along the center line of said piston ring, a pair of moreor less parallel, integrally formed extensions projecting from each ofsaid troughs radially outward beyond said crests, the members of eachpair of said extensions extending in generally opposite circumferentialdirections from the point of juncture with said troughs, said extensionsforming a pair of more or less continuous, axially-separated, annular,cylinder-contacting ribs said extensions being substantially axiallyspaced from said crests and permitting radial passage of lubricantacross said crests.

2. A one-piece, flexible, self-expanding piston ring comprising acentral, corrugated annulus composed of alternating crests and troughsof spring material extending in a generally radial direction, saidcrests being radially outermost and consisting of relatively narrowstrips placed along the center line of said piston ring, a pair ofprojections extending in opposite axial directions from each of saidcrests, a pair of more or less parallel, integrally formed extensionsprojecting from each of said troughs radially outward beyond saidcrests, the members of each pair of said extensions extending ingenerally opposite circumferential directions from the point of juncturewith said trough, said extensions forming a'pair of more or lesscontinuous,

axially-separated, annular, cylinder-contacting 4 ribs and beingsupported against axially inward displacement by said projections.

3. A one-piece, flexible, self-expanding, piston ring comprising acentral, corrugated annulus composed of alternating crests and troughsof spring material extending in a generally radial direction, saidcrests being radially outermost and consisting of relatively narrow,axially-centered strips, a pair of projections extending in oppositeaxial directions irom each of said crests, a pair of more or lessparallel, integrally formed extensions projecting from each of saidtroughs radially outward beyond said crests, each member of a pair ofsaid extensions having a larger circumferential dimension in thegenerally opposite direction than the other member of said pair, saidextensions forming a pair of more or less continuous, axially-separated,annular, cylinder-contacting ribs and being supported against axiallyinward displacement by said projections. I

4. A flexible, self-expanding piston ring comprising a centralcorrugated annulus composed of alternating crests and troughs of springmaterial extending in a generally radial direction, said crests beingradially outermost and consisting ofrelatively narrow, axially-centeredstrips, 9, pair of projections extending in opposite axial directionsfrom each of said crests, a pair of more or less parallel, integrallyformed extensions projecting from each of said troughs radially outwardbeyond said crests, said extensions being circumferentially staggered,said extensions forming a pair of more or less continuous,axially-separated, annular, cylinder-contacting ribs.

5. A self-expanding, flexible piston ring formed of a series ofgenerally adjacent sections each including a pair of generally parallelside walls, and a back panel formed integrally with said side walls andforming a generally U-shaped cross-section in an axial plane, arelatively narrow, axially-centered spring member connecting successivepairs of adjacent sections, said spring members being formed integrallywith and in continuation of said back panel, said pairs of side wallsforming a pair of more or less continuous, axially-separated, annular,cylindercontacting ribs, said narrow spring members being substantiallyaxially spaced from the planes of said ribs to permit radial passage oflubricant across said spring members,

6. A self-expanding, flexible piston ring formed of a series ofgenerally adjacent sections each including a pair of generally parallelside walls, each of said side walls having a larger dimension in agenerally opposite circumferential direction than the other side wall,and a back panel formed integrally with said side walls and forming agenerally U-shaped cross-section in an axial plane, a relatively narrow,axially-centered spring member connecting successive pairs of adjacentsections, said spring members being formed integrally with and incontinuation of said back panel and extending radially outward betweensaid side walls, a pair, of projections extending in opposite axialdirections from each of said spring members, said pairs of side wallsforming a pair of more or less continuous, axiallyseparated, annular,cylinder-contacting ribs and being supported against axially inwarddisplacement by said projections.

7. A piston ring comprising spaced-apart sides made up of a plurality ofseparated segments, each of said segments being ,supported by a web,said webs being spaced apart and integral with and supported by acontinuous intermediate body portion which extends circumferentially ofthe ring in spaced relation to the sides.

8. A split piston ring comprising a central supporting strip of pistonring material, said central supporting strip extending withoutinterruption circumferentially of the ringbetween the ends thereofspaced-apart resilient web portions extending from opposite sides of thestrip in a direction axially of the ring, said web portions supporting aplurality of contiguously arranged segments which form land surfaces ofthe ring, each of said segments and a respective web portion beingmovable independently of the remaining segments and their respective webportions.

9. A split piston ring comprising upper and lower sides, said sideshaving radially extending openings which define spaced-apart crowns, acontinuous central body portion, web portions extending from one edge ofthe central body portion to connect with crowns of the said upper sideof the ring and other web portions extending from an opposite edge ofthe central body portion to connect with crowns at the said lower sideof the ring.

CARL F. ENGELHARDT.

